During cutting operations discussed above, a large amount of dusts and/or debris may be generated from cutting area. In order to satisfactorily maintain a working environment, it is necessary to prevent the generated dusts and/or debris from being scattered around. Owing to this, during the cutting operations, a dust collection cover (a dust collector) is attached to a cutting device. A technique relating to the dust collection cover (dust collector) is disclosed in the following patent documents.
Japanese Laid-Open Patent Publication No. 2007-30314 discloses a dust collection cover which supports a cutting device having a rotary cutting blade such as a diamond cutter so as to be vertically moved with respect to a fixing cover supported on a base with which a cutting surface of a material to be cut is brought into contact. According to this dust collection cover, a grooving operation or a cutting operation can be performed by moving the rotary cutting blade within the fixing cover downward so as to protrude below a bottom surface of the base and then cutting a material to be cut with the protruding portion of the rotary cutting blade. This type of cutting is called a plunge cut.
U.S. Patent Publication No. 2008-0244910 discloses a dust collection cover used for the same kind of a cutting device, especially a dust collection cover with a double structure which supports a main body cover attached to a cutting device so as to be moved in an upward and downward direction with respect to a fixing cover supported on a base with which a cutting surface of a material to be cut is brought into contact. In the dust collection cover with the double structure, a cutting operation such as grooving can be performed by moving the cutting device together with the main body cover downwards so as to protrude the rotary cutting blade below a bottom surface of the base and then cutting a cutting surface of a material to be cut with the protruding cutting blade. According to the dust collection cover with the double structure, the main body cover is overlapped with the fixing cover, and accordingly, compared to the former dust collection cover, a higher sealability (high dust collection efficiency and/or strong dust collection power) of the dust collection cover with respect to the dusts and/or debris generated around a tip of the rotary cutting blade can be obtained along an overall vertical movable range of the rotary cutting blade.
However, it has been necessary to further improve the above latter dust collection cover with the double structure. In the prior art disclosed in U.S. Patent Publication No. 2008-0244910, it is configured that the main body cover is supported so as to be rotated via a rotary support shaft in front of the fixing cover and that the main body cover (the cutting device) is biased toward an upward direction (in a direction such that the rotary cutting blade does not protrude below the bottom surface of the base) by a torsion spring attached to or around the rotary support shaft. Because the torsion spring for biasing the main body cover (the cutting device) is attached to or around the rotary support shaft, it may be difficult to set a rotation range of the cutting device to be large. When the cutting device is returned to an upper position, the rotary cutting blade is covered with the fixing cover and the main body cover.
Because of this construction, when replacing the rotary cutting blade, the rotary support shaft and the torsion spring must be disassembled to separate the cutting blade from the fixing cover together with the main body cover. Thus, when attaching the main body cover to the fixing cover after the rotary cutting blade is replaced, it may take time to reassemble the torsion spring in a predetermined condition, which may be awkward and troublesome for a user. In this respect, it has been necessary to improve operability in replacing the rotary cutting blade.
Thus, regarding the dust collection cover with the double structure, in which a cutting area of the material to be cut is covered with the fixing cover and the main body cover, there is a need in the art to improve operability mainly in replacing the rotary cutting blade.
Furthermore, according to the dust collection cover in the above prior art, it may not be possible to finely adjust a cutting depth of the rotary cutting blade with respect to a cutting surface of the material to be cut. Thus, there is a need in the art to improve operability in adjusting the cutting depth with respect to a cutting surface of the material to be cut in a cutting device referred to as a plunge cutter, or more specifically, in a cutting device having a dust collection cover with the double structure in which a cutting area of the material to be cut is covered with the fixing cover and the main body cover.
Furthermore, the dust collection cover in the above prior art has not provided with a mechanism for easily and reliably locking an opening/closing operation of the main body cover with respect to the fixing cover at an arbitrary (opening/closing) angle. Thus, there is a need in the art to easily and reliably lock the main body cover with respect to the fixing cover at an arbitrary (opening/closing) angle.